Resistor and method of making the same



Dec. 26, 1950 G. J. MUCHER 2,535,803

RESISTOR AND METHOD OF MAKING THE SAME Filed May 13, 1948 mmq 7 JNVENTOR. 6011 6 I fluriwr Ma i/ 14T70RNEYS Patented Dec. 26, 1950 RESISTOR AND METHOD OF MAKING THE SAME George J. Mucher, Brooklyn, N. Y., assignor to *Clarostat Mfg. 00., 1110., Brooklyn, N. Y., a corporation of New York Application May 13, 1948, Serial No. 26,763

3 Claims.

This invention relates to electrical resistance devices, and particularly to high-wattage wirewound resistors.

Resistors embodying wire-wound rigid cores encased in ceramic tubes or coated with inorganic cement are widely used because the absence of organic materials in their construction makes them inherently capable of high-wattage ratings. However, the cost of manufacture of such resistors is relatively large because even in volume production, each core must be individually wound and handled.

A resistor made according to the present invention provides the high-wattage rating of conventional inorganic rigid core resistors, but is susceptible of mass production and correspondingly reduced manufacturing costs. Instead of a limited length ceramic core on which the resistance wire is wound, I apply the winding to an indefinite length of flexible inorganic strand such as a fiberglass cord. Such a resistance element may be wound on conventional automatic winding machines and may have a length of five hundred feet or more; the length is limited only by the available length of the strand. The wound core may be rewound on reels and stored for future use. It is subsequently only necessary to cut the strand to appropriate lengths, afiix terminals and place the unit within a suitable enclosure, all as hereinafter described.

It is therefore an object of the invention to provide an inexpensive resistor formed entirely of inorganic material, and capable of highwattage performance.

It is another object of the invention to provide a resistance element capable of mass production and resultant low manufacturing costs.

It is a still further object of the invention to provide an improved method of manufacturing high-wattage rating resistors.

Other features and advantages will hereinafter appear.

In the accompanying drawings Fig. 1 is a side elevation of a resistor constructed pursuant to the present invention;

Fig. 2 is a somewhat schematic representation of a core strand partially wound with resistance wire; I

Fig. 3 is a longitudinal section of a completed resistor, and

Fig. 4 is a somewhat schematic representation of a method of forming the resistor.

Fig. 1 shows aside elevation of a resistor In in which an outer tube H of glass, ceramic, or other inorganic insulation material contains a resistance element |2 (see Fig. 3) from which extend the terminal wires M, M. The resistance element comprises as in Fig. 2 a flexible body |5 of inorganic material, such as a fiberglass cord on which is wound, pursuant to conventional winding practices, a resistance wire l6 having suitable characteristics.

Fig. 2 represents only a fragment of a length the cord |5 which may, in a continuous operation, be Wound with resistance wire and have a total length of five hundred feet or more. The thuswound core may be reeled and stored for future use.

When the thus-prepared resistance is to be fabricated into the final resistor, the necessary lengths are cut and terminal caps H, with the leads |4 aflixed thereto, are applied to the ends of the sections. The caps may be initially cylindrical and are conveniently crimped about the resistance element for securement thereon and for good electrical connection with the winding I6.

The resistance element I2 is then placed within the tube H and an inorganic, preferably coldsetting, cement filling is applied. This may advantageously be done in a fixture schematically shown in Fig. 4. The tube H is placed within a suitable cavity in an extrusion head 20, said head having a passage 2| communicating with which is a conduit 22 connecting with a suitable reservoir of cement. The cement is preferably a rather thick slurry, and suitable means (not shown) are provided to eject it into the passage 2| under pressure, whence it flows into the tube H and about the resistance element I2, spacing said element within from the inner wall of the tube and securing it therein. The length of the cavity 2| is preferably so related to the length of the connector lead wire l4, that when the tube is placed within the cavity with the wire resting upon the bottom of the cavity, the resistor unit I2 will be centered with respect to the length of the tube A fixture 23 has an abutment 24 which will be engaged by the end of the opposite terminal wire M to prevent lateral movement of the element l2 during the cement filling operation. The resultant cement filling 25 secures the unit |2 within the tube H and maintains the coils of the winding in mutually insulated relationship.

The unit |0 may then be removed from the extrusion head and cleaned of excess cement, following which it is permitted to stand at atmospheric temperature until the mass of 3 cement 25 has hardened. The resistor is then ready for use.

Thus, among others, the several objects of the invention as aforenoted are achieved. Obviously numerous changes in construction and rearrangement of the parts might be resorted to without departing from the spirit of the in' vention as defined by the claims. Also the steps of the method might be varied without departing from the spirit of the invention.

I claim: H

l. A method of making electrical "resistances which includes providing a resistance element embracing a wire-wound flexible-body,.applying wire-carrying terminal caps'to thelends thereoi, indenting the outer surfaces of the caps to constrict the same into electricalcontact with the adjacent windings to furnish a body assembly with the cap-carried wires extending outwardly and axially therefrom, employing a tube of inorganic insulating material having an overall length and internal 'diametergreater than the said assembly, introducing the latter into said tube to cause the Winding of said body to be spaced from the inner tube face and with the capshoused in the tube at; points short of the ends therof, disposing thetubeto extend in a non-horizontal position and-introducing through the lower tube end a mass of insulating cement to a volume such that the spaces between the assembly and tube ends is completely filled and the cement extends into the-cap indentations; the cap-carrying wires extending beyond the ends of the latter.

2. .A resistor comprising afiexiblecore of insulating material, a coil of wire wound around said .core and extending to the ends thereof, caps encasing the ends of said core and constricted around the coil convolutions adjacent such ends to intimately engage the .same, terminal leads extending outwardly of and secured to said caps, a tube having a length and bore diameter in excess of the length and external diameter of the core and cap assembly, the tube being concentrically disposed and spaced fromthe core and the latter having its outer cap sur- 'faces lying at points short of the tube ends, a layer of insulating cement completely filling the 4 space between said tube and core and extending beyond the outer cap surfaces to maintain all parts of the resistor assembly against movements with respect to each other and said terminal means projecting through the cement layer beyond the cap surfaces.

3. Aresistor comprising afiexible'core of insulating material, a coil ofwire wound around said core and extending to the ends thereof, caps encasing the ends of said core and crimped into contact with the coil convolutions adjacent such ends to intimately engage the same and constrict the coils and core body in line with such crimping, terminal leads extending downwardly 'of and secured to said caps, a tube having length andbore diameter in excess of the length and external diameter of the core and cap assembly,

the tube being concentrically disposed and spaced from the core and the latter having its outer cap surfaces lying at points short of the tube ends, a layer of insulating cement completely filling the space between said tube andcore and extending into the cap crimping and beyond the outer capsurfaces to maintain all parts of the resistor assembly against movements with .respect to each other and said terminal leads projecting through the cement layer beyond the cap surfaces.

GEQRGE J.

REFERENCES CITED I The following references are of record in the file of this patent:

UNITED STATES PATENTS 

